//! Windows-specific file system event handling

use super::EventHandler;
use crate::infra::event::{Event, FsRawEventKind};
use crate::service::watcher::event_handler::WatcherEventKind;
use crate::service::watcher::{WatchedLocation, WatcherEvent};
use anyhow::Result;
use std::collections::HashMap;
use std::path::PathBuf;
use std::sync::Arc;
use std::time::{Duration, Instant};
use tokio::sync::RwLock;
use tracing::{debug, trace, warn};
use uuid::Uuid;

/// Windows-specific event handler that handles Windows filesystem quirks
pub struct WindowsHandler {
	/// Recently processed events for debouncing
	recent_events: Arc<RwLock<HashMap<PathBuf, Instant>>>,
	/// Files pending deletion (Windows has delayed deletion)
	pending_deletions: Arc<RwLock<HashMap<PathBuf, Instant>>>,
	/// Debounce duration
	debounce_duration: Duration,
}

impl WindowsHandler {
	pub fn new() -> Self {
		Self {
			recent_events: Arc::new(RwLock::new(HashMap::new())),
			pending_deletions: Arc::new(RwLock::new(HashMap::new())),
			debounce_duration: Duration::from_millis(200), // Windows needs more debouncing
		}
	}

	/// Check if event should be debounced
	async fn should_debounce(&self, path: &PathBuf) -> bool {
		let mut recent = self.recent_events.write().await;
		let now = Instant::now();

		if let Some(&last_seen) = recent.get(path) {
			if now.duration_since(last_seen) < self.debounce_duration {
				return true;
			}
		}

		recent.insert(path.clone(), now);

		// Cleanup old entries
		recent.retain(|_, &mut last_seen| now.duration_since(last_seen) < Duration::from_secs(2));

		false
	}

	/// Handle Windows-specific delayed deletion detection
	async fn handle_delayed_deletion(&self, path: &PathBuf) -> bool {
		// On Windows, files can appear to be deleted but still be accessible
		// for a short time due to file locking, antivirus, etc.
		match tokio::fs::metadata(path).await {
			Ok(_) => {
				// File still exists, might be a false deletion event
				let mut pending = self.pending_deletions.write().await;
				pending.insert(path.clone(), Instant::now());
				false // Don't process deletion yet
			}
			Err(_) => {
				// File actually doesn't exist
				let mut pending = self.pending_deletions.write().await;
				pending.remove(path);
				true // Process deletion
			}
		}
	}

	/// Process pending deletions that have timed out
	async fn process_pending_deletions(
		&self,
		watched_locations: &Arc<RwLock<HashMap<Uuid, WatchedLocation>>>,
	) -> Result<Vec<Event>> {
		let mut events = Vec::new();
		let mut pending = self.pending_deletions.write().await;
		let now = Instant::now();

		let mut to_remove = Vec::new();
		for (path, timestamp) in pending.iter() {
			if now.duration_since(*timestamp) > Duration::from_millis(500) {
				// Check if file still doesn't exist
				if tokio::fs::metadata(path).await.is_err() {
					// File is definitely gone, emit deletion event
					let locations = watched_locations.read().await;
					for location in locations.values() {
						if location.enabled && path.starts_with(&location.path) {
							events.push(Event::FsRawChange {
								library_id: location.library_id,
								kind: FsRawEventKind::Remove { path: path.clone() },
							});
							break;
						}
					}
				}
				to_remove.push(path.clone());
			}
		}

		for path in to_remove {
			pending.remove(&path);
		}

		Ok(events)
	}

	/// Handle Windows-specific temporary file patterns
	fn is_windows_temp_file(&self, path: &PathBuf) -> bool {
		let path_str = path.to_string_lossy().to_lowercase();

		// Windows common temporary file patterns
		path_str.contains("~$") || // Office temp files
        path_str.ends_with(".tmp") ||
        path_str.ends_with(".temp") ||
        path_str.contains(".crdownload") || // Chrome downloads
        path_str.contains(".part") || // Firefox downloads
        path_str.contains("thumbs.db") ||
        path_str.contains("desktop.ini") ||
        path_str.contains("$recycle.bin")
	}
}

#[async_trait::async_trait]
impl EventHandler for WindowsHandler {
	async fn process_event(
		&self,
		event: WatcherEvent,
		watched_locations: &Arc<RwLock<HashMap<Uuid, WatchedLocation>>>,
	) -> Result<Vec<Event>> {
		if !event.should_process() {
			return Ok(vec![]);
		}

		let mut events = Vec::new();

		for path in &event.paths {
			// Skip Windows-specific temporary files
			if self.is_windows_temp_file(path) {
				trace!("Skipping Windows temp file: {}", path.display());
				continue;
			}

			// Check for debouncing
			if self.should_debounce(path).await {
				debug!("Debounced event for: {}", path.display());
				continue;
			}

			let locations = watched_locations.read().await;
			for location in locations.values() {
				if !location.enabled || !path.starts_with(&location.path) {
					continue;
				}

				match &event.kind {
					WatcherEventKind::Create => {
						events.push(Event::FsRawChange {
							library_id: location.library_id,
							kind: FsRawEventKind::Create { path: path.clone() },
						});
						trace!("Windows: Created {}", path.display());
					}
					WatcherEventKind::Modify => {
						events.push(Event::FsRawChange {
							library_id: location.library_id,
							kind: FsRawEventKind::Modify { path: path.clone() },
						});
						trace!("Windows: Modified {}", path.display());
					}
					WatcherEventKind::Remove => {
						// Handle Windows delayed deletion
						if self.handle_delayed_deletion(path).await {
							events.push(Event::FsRawChange {
								library_id: location.library_id,
								kind: FsRawEventKind::Remove { path: path.clone() },
							});
							trace!("Windows: Removed {}", path.display());
						} else {
							trace!("Windows: Pending deletion for {}", path.display());
						}
					}
					WatcherEventKind::Rename { from, to } => {
						events.push(Event::FsRawChange {
							library_id: location.library_id,
							kind: FsRawEventKind::Rename {
								from: from.clone(),
								to: to.clone(),
							},
						});
						trace!("Windows: Renamed {} -> {}", from.display(), to.display());
					}
					_ => {
						trace!("Windows: Unhandled event type for {}", path.display());
					}
				}
				break;
			}
		}

		Ok(events)
	}

	async fn tick(&self) -> Result<()> {
		// Clean up recent events
		let mut recent = self.recent_events.write().await;
		let now = Instant::now();
		recent.retain(|_, &mut last_seen| now.duration_since(last_seen) < Duration::from_secs(5));

		Ok(())
	}
}

/// Additional method for Windows handler to process pending deletions
impl WindowsHandler {
	pub async fn tick_with_locations(
		&self,
		watched_locations: &Arc<RwLock<HashMap<Uuid, WatchedLocation>>>,
	) -> Result<Vec<Event>> {
		// Process any pending deletions
		self.process_pending_deletions(watched_locations).await
	}
}

#[cfg(test)]
mod tests {
	use super::*;
	use std::time::SystemTime;

	#[tokio::test]
	async fn test_windows_handler_creation() {
		let handler = WindowsHandler::new();
		assert_eq!(handler.debounce_duration, Duration::from_millis(200));
	}

	#[tokio::test]
	async fn test_windows_temp_file_detection() {
		let handler = WindowsHandler::new();

		// Should detect Windows temp files
		assert!(handler.is_windows_temp_file(&PathBuf::from(r"C:\temp\~$document.docx")));
		assert!(handler.is_windows_temp_file(&PathBuf::from(r"C:\temp\file.tmp")));
		assert!(handler.is_windows_temp_file(&PathBuf::from(r"C:\temp\Thumbs.db")));
		assert!(handler.is_windows_temp_file(&PathBuf::from(r"C:\temp\desktop.ini")));

		// Should not detect normal files
		assert!(!handler.is_windows_temp_file(&PathBuf::from(r"C:\temp\document.docx")));
		assert!(!handler.is_windows_temp_file(&PathBuf::from(r"C:\temp\image.jpg")));
	}

	#[tokio::test]
	async fn test_debounce_logic() {
		let handler = WindowsHandler::new();
		let path = PathBuf::from(r"C:\test\file.txt");

		// First event should not be debounced
		assert!(!handler.should_debounce(&path).await);

		// Second immediate event should be debounced
		assert!(handler.should_debounce(&path).await);
	}
}
